Air homogenizer for respiratory gas analysis equipment

ABSTRACT

An air homogenizer device comprising an enclosure defining a chamber formed with an inlet opening and an outlet port, and a mixer conduit within the chamber forming the crossbar of a Tshaped pipe configuration. The other leg of the &#39;&#39;&#39;&#39;T&#39;&#39;&#39;&#39; is an input conduit connecting the center of the mixer conduit to the inlet opening of the chamber. The chamber has a removable lid formed with a central opening which receives a fan motor having a drive shaft depending therefrom. A fan blade on the shaft and a surrounding annular duct cooperate to draw air from an exit port formed in the mixer conduit, causing air within the chamber to be drawn into an entrance port. The resulting flow entrains and draws air from the input conduit into the mixer conduit, and there blends it homogeneously with the air previously contained in the chamber.

United States Patent [72] Inventor Donald B. Falk East Seaford, N.Y.

[21] Appl. No. 7,7804

[22] Filed Feb. 2, 1970 [45] Patented Oct. 12, 1971 [73] Assignee Instrumentation Associates lnc.

New York, N.Y.

[54] AIR HOMOGENIZER FOR RESPIRATORY GAS ANALYSIS EQUIPMENT 6 Claims, l Drawing Fig.

[52] U.S. Cl 12S/2.07, 73/23, 98/38 [5l] Int. Cl A61b5/00 [50] Field of Search 12B/2.07,

[56] References Cited UNITED STATES PATENTS 2,192,799 3/1940 Perrill 12B/2.07

2,824,621 2/1958 Carrier 261/30 X 2,873,908 2/1959 Powers 261/30 X Primary Examiner- Richard A. Gaudet Assistant Examiner-Kyle L. Howell Attorneys--Donald E. Nst and Jay H. Quartz ABSTRACT: An air homogenizer device comprising an enclosure defining a chamber formed with an inlet opening and an outlet port, and a mixer conduit within the chamber forming the crossbar of a T-shaped pipe configuration. The other leg of the 'I`" is an input conduit connecting the center of the mixer conduit to the inlet opening of the chamber. The chamber has a removable lid formed with a central opening which receives a fan motor having a drive shaft depending therefrom. A fan blade on the shaft and a surrounding annular duct cooperate to draw air from an exit port fon'ned in the mixer conduit, causing air within the chamber to be drawn into an entrance port. The resulting flow entrains and draws air from the input conduit into the mixer conduit, and there blends it homogeneously with the air previously contained in the chamber.

PATENTE DCT] 21971 3,612039 INVENTQR By DONALD B. FALK ATTORNEYS.

AIR- HOMOGENIZER FOR RESPIRATORY GAS ANALYSIS EQUIPMENT FIELD OF THE INVENTION This invention relates generally to equipment for gas composition analysis, and is specifically concerned with a device for producing homogeneous gas mixtures for use in a medical lung function analyzer.

THE PRIOR ART As the problem of air pollution in urban areas has worsened, respiratory difficulties have become a leading medical problem. ln dealing with illnesses of the respiratory tract, the

medical profession often resorts to lung function analyzers which are designed to capture the air exhaled by a patient, and` analyze its contents to determine the concentration of biologically significant components such as nitrogen and carbonv dioxide. These devices typically have gas concentration readouts which reset at regular intervals, so that changes in gas concentration which occur during a test may be observed.

In the past, however, some lung function analyzers have responded too quickly and sensitively to changes in the composition of exhaled air, causing the readout to fluctuate rapidly and thus give the medical investigator the impression that a significant change in gas concentration has occurred, when in fact the analyzer is responding only to short term changes or random fluctuations.

THE INVENTION which communicate with the interior of the chamber. A pair of inlet openings are formed in the wall of the chamber and the wall of the mixer conduit respectively, the inlet opening of the mixer conduit being located intermediate the entrance and exit ports thereof. An input conduit is provided, which has ports that communicate respectively with the two inlet openings, so that air introduced through the input conduit is connected to an intermediate region of the interior of the mixer conduit. Finally, means are providedfor causing the air within the chamber to flow through the mixer conduit from the entrance port to the exit port thereof, so that the air in the input conduit becomes entrained in the flow of air through the mixer conduit, and thereby mixes homogeneously therewith. Ultimately, the contents of the chamber leave by way of the outlet port and enter the lung function analyzer. But by that time, the air passing through the chamber outlet port contains a random mixture of air exhaled at different time intervals.

Thus, only those changes in gas concentration which persist over a significant period of time can cause detectable changes in the response of the lung function analyzer.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing is a vertical section of anair-homogenizing device in accordance with this invention, along with suitable tubing connected to the inlet and outlet ports thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in the drawings, the device of this invention comprises u chamber, generally designated l0, which includes a cylindrical vessel l2 open at its upper end, and a circular lid 14 closing olf the open end of the vessel. At its outer periphery, the lid 14 is formed with a depending annular flange I6 which surrounds the open end of the vessel 12 for sealing purposes. An annular metal band l8 surrounds the vessel l2, and is fixed thereto immediately below the lid flange 16. The band I8 is formed with an upper edge which is spaced away from the wall of the vessel 12 in order to receive the lid flange 16 for mechanical assembly and air-sealing purposes.

The wall of vessel l2 is formed with an opening 20 which defines an outlet port for the air contained therein. This port 20 is fitted with an annular sealing grommet 22 made of a rubbery material. The central opening of the grommet receives a short length of pipe 24 defining an outlet conduit for the chamber l0, the pipe 24 and grommet 22 being in sealing relationship with each other. An appropriate length of hose 26 tits over the outlet pipe 24, and leads ultimately to a device which utilizes the output of the air homogenizer. In a typical application, the utilizing device would be a medical lung function analyzer.

Suitably mounted within the chamber l0, as by press fitting into an opening in container l0 is a horizontal pipe 38. Fixed to pipe 38, as by welding or the like, is a vertical mixer tube 30l which is open at its opposite ends to define entrance and exit ports 32and 34 respectively. As can be seen, tube 30 is joined to pipe 38 at a location intermediate these entrance and Aexit ports, and the two communicate through van inlet opening36. The two tubes 30 and 38 form a T-shaped configuration, the tube 38 being sealed in some appropriate manner to the intermediate opening 36 of the tube`30. The tube 38 is in effect an input conduit having a pair of opposed ports 40 and 42 at its opposite ends, the port 40 communicating with the inlet opening 36.

The vessel l2 of chamber l0 is formed with an inlet opening 50 of its own, located diametrically opposite the outlet opening20. This opening 50 is sealed by a resilient annular sealing grommet S2 similar to the grommet 22 which seals the outlet opening. The end of the input tube 38 extending away from the mixer tube 30 passes through the center of the grommet 52 in sealing relationship therewith, so that the port 42 is situated externally of the chamber l0. A length 54 of the input tube 38 projects suiciently beyond the wall of the vessel l2 to provide a connecting collar, to which an intake hose 56 can be attached.

lt will be readily appreciated that air introduced into the intake hose 56 is conducted to the port 42 and then through the input tube 38 to the port 40 thereof. From there it passes through the inlet opening 36 and enters the intermediate region of the mixer tube 30, later finding its wayy out of the tube 30 and into the chamber l0. The relationship between the grommet S2 and the projecting end 54 of tube 38 effectively seals the chamber inlet opening 50 against the introduction of air into the interior of the chamber l0 through any other pathway. The lid 14 serves a similar function with respect to the open top of the vessel l2.

The central region of the lid I4 is formed with a circular opening 60 which is coaxial with the mixer tube 30, the edges of the opening 60 being bent down to form a depending annular flange 62. An electric motor 64, suitable for driving a smally fan blade 66, is tightly received within the opening 60y and flange 62, the tightfit serving both as a means of preventing air from entering the chamber l0 through the lid opening 60, and also as a means of mounting the fan motor 64. A drive shaft 68 depends from the fan motor 64 coaxially with the mixer tube 30, and serves for both mounting and driving the fan blade 66. A pair of electrical leads 70 emerge from the fan motor 64 externally of the chamber l0, and may be connected to a suitable power source for driving the motor. This construction thus avoids any necessity for passing the electrical leads 70 through an opening in the walls of the chamber, an expedient which would present additional problems of sealing the chamber against the entrance of ambient air` The function of the fan blade 66 is to draw air upwardly from the mixer tube.30 and out the exit port 34 thereof, as indicated by the arrows 72; with the result that the air is subsequently ejected upwardly by the fan blade 66 and caused to circulate, as indicated by arrows 74, into the region of the interior of the chamber Il() surrounding the mixer tube 30. At the same time, other air from the interior of the chamber l is drawn upwardly, as indicated by arrows 76, through the entrance port 32 and into the interior of the mixer tube 30 to replace the air thus withdrawn.

ln order to make the fan blade 66 more efficient in performing this function, it is surrounded by an annularly-shaped duct 80, mounted coaxially with the mixer tube 30 (by means not illustrated). The blade 66, when surrounded by the annular duct 80, becomes in effect a ducted fan which, it is well known, has the effect of confining the intake of the fan blade to a directional path extending directly downward from the duct 80 in a direction coaxial therewith. The duct 80 is also tapered as seen at 82 to form an entrance 84 which is of approximately the same diameter as the mixer tube exit port 34, and which is situated closely adjacent thereto and positioned coaxially therewith. As a result, essentially all of the air intake of the fan blade 66 is drawn from the mixer tube 30 through the exit pon 34 thereof, and enters the duct 80 through the entrance 84. The efficiency of the fan blade 66 in evacuating air from the mixer tube 30 is thus greatly enhanced, making the air homogenizer of this invention quite effective in blending the contents of the mixer tube 30 with the contents of the chamber surrounding the mixer tubeA The flow of air within the vessel l0, which is vertically upward through the mixer tube 30 as indicated by the arrows 76 and 72, creates a Bernoulli vacuum which draws air from the input tube 38 through the port 40 and inlet opening 36 into the intermediate region of the mixer tube 30, as indicated by arrow 90. The air represented by the arrow 90 thus becomes entrained within the stream represented by the arrows 76 and 72, and consequently mixes thoroughly therewith. As a result, the air emerging from the mixer tube 30 and circulating into the surrounding region of the enclosed chamber l0, as indicated by arrows 74, comprises a homogeneous mixture of the air entering the mixer tube by way of the entrance port 32 and the air entering the mixer tube by way of the input tube 38. The blending of the airflow indicated by arrow 90 with the airflow indicated by arrows 72 is inherently a random process, and the randomizing is later enhanced by the turbulence generated by the spinning of the fan blade 66.

Because of the partial vacuum created at the junction of tubes 38 and 30, additional air is drawn through the intake hose 56 and input tube 38, as indicated by arrows 92. Thus the process of blending the two streams continues indefinitely as long as the fan blade 66 continues to rotate. The result is a continuous process of forced homogenization of air taken in through the intake hose 56 with the air previously contained within the chamber l0 and mixer tube 30. ln order to make room for the air drawn in through the intake hose S6, an equal volume of air leaves, as indicated by arrows 94, through the outlet port and connecting tube 24. This exiting volume of air is conducted to the lung function analyzer by the output hose 26.

The intake hose 56 is connected to a patients breathing mask, so that the input stream represented by the arrows 92 consists of air exhaled by the patient. Thus the device of this invention serves as a homogenizer for blending recently exhaled air with air previously exhaled by the same patient. At any moment, the contents of the chamber l0 and mixer tube 30 represent a volume of air exhaled by the patient over a preceding time interval, while the air presently entering homogeneous'mixture of air exhaled over a period of time. As a resu t, the arr delivered to the lung function analyzer by the output hose 26 has a composition which represents an integration of the composition of the patients breath as it varies over that period of time, and short term or random fluctuations are thereby smoothed out and eliminated from consideration.

What is claimed is:

l. A device for forced homogenization of gas for use in combination with respiratory gas analysis equipment, comprising:

an enclosed chamber having an outlet port for communication with said gas composition analysis equipment;

a mixer conduit mounted within said chamber, said mixer conduit having entrance and exit ports, both of which communicate with the interior of said chamber;

respective inlet openings formed in the exterior walls of said chamber and said mixer conduit, said mixer conduit inlet opening being intermediate said entrance and exit ports;

an input conduit having a pair of ports communicating respectively with said inlet openings of said chamber and said mixer conduits said input conduit leading from said inlet opening of said chamber into an intermediate region of the interior of said mixer conduit and adapted to be connected to a patients exhalation conduit;

and means for causing gas within said chamber to flow through said mixer conduit from said entrance port to said exit port thereof, whereby gas from said input conduit becomes entrained in the flow of gas through said mixer conduit and mixes homogeneously therewith.

2. A device as in claim l wherein:

said mixer conduit has a substantially tubular configuration with axially opposed openings at either end defining said entrance and exit ports thereof.

3. A device as in claim 2 wherein:

said respective inlet openings are aligned substantially coaxially with each other;

and said mixer and input conduits form a T-shaped pipe.

4. A device as in claim 2, wherein said flow-causing means comprises:

a fan blade situated in proximity to one of said end openings of said mixer conduit',

and means mounting and driving said fan blade for rotation about the axis of said mixer conduit.

5. A device as in claim 4, further comprising:

annular duct means mounted substantially coaxially with said mixer conduit, and surrounding said fan blade whereby to confine the gas intake of said fan blade largely to said mixer conduit.

6. A device as in claim 4, wherein:

said chamber comprises a removable and replaceable lid;

said lid is formed with an opening aligned with the axis of said mixer conduit;

and said fan means comprises a fan motor which is secured within said lid opening, and has a drive shaft extending therefrom substantially coaxially with said mixer conduit',

and said fan blade is secured to said drive shaft. 

1. A device for forced homogenization of gas for use in combination with respiratory gas analysis equipment, comprising: an enclosed chamber having an outlet port for communication with said gas composition analysis equipment; a mixer conduit mounted within said chamber, said mixer conduit having entrance and exit ports, both of which communicate with the interior of said chamber; respective inlet openings formed in the exterior walls of said chamber and said mixer conduit, said mixer conduit inlet opening being intermediate said entrance and exit ports; an input conduit having a pair of ports communicating respectively with said inlet openings of said chamber and said mixer conduits said input conduit leading from said inlet opening of said chamber into an intermediate region of the interior of said mixer conduit and adapted to be connected to a patient''s exhalation conduit; and means for causing gas within said chamber to flow through said mixer conduit from said entrance port to said exit port thereof, whereby gas from said input conduit becomes entrained in the flow of gas through said mixer conduit and mixes homogeneously therewith.
 2. A device as in claim 1 wherein: said mixer conduit has a substantially tubular configuration with axially opposed openings at either end defining said entrance and exit ports thereof.
 3. A device as in claim 2 wherein: said respective inlet openings are aligned substantially coaxially with each other; and said mixer and input conduits form a T-shaped pipe.
 4. A device as in claim 2, wherein said flow-causing means comprises: a fan blade situated in proximity to one of said end openings of said mixer conduit; and means mounting and driving said fan blade for rotation about the axis of said mixer conduit.
 5. A deVice as in claim 4, further comprising: annular duct means mounted substantially coaxially with said mixer conduit, and surrounding said fan blade whereby to confine the gas intake of said fan blade largely to said mixer conduit.
 6. A device as in claim 4, wherein: said chamber comprises a removable and replaceable lid; said lid is formed with an opening aligned with the axis of said mixer conduit; and said fan means comprises a fan motor which is secured within said lid opening, and has a drive shaft extending therefrom substantially coaxially with said mixer conduit; and said fan blade is secured to said drive shaft. 